The Camp Nou supremo insists the Argentine remains their main man and discussed the difficult decision to allow Eric Abidal and David Villa to depart
The €57 million (£50m) acquisition of the Brazil starlet lead to club legend Johan Cruyff to suggest that Messi should be sold as the duo would not be able to function well in the same side, but Rosell has shrugged off such a notion.
"There are not two roosters in the hen-house. There is one, and he is Messi," he told Catalan TV station 8TV. "Now we've signed Neymar, a great player and a great person. There is no-one better than Messi, but Neymar comes to show he is a great player and can help Barca."
Neymar's arrival prompted the exit of Spain forward David Villa, who joined Atletico Madrid in a €5.1m deal (£4.3m), and Rosell believes the move was in the best interests of both clubs and the 31-year-old himself.
"The amount of Euros for the salary are as important as those of the transfer, the length of the contract and the player's age," he continued.
"Villa knows that, if he had stayed, he might not have played the minutes he would have liked. It has therefore been a very large operation for Barca and a great one for Villa and Atletico."
Eric Abidal was another veteran to depart Camp Nou this summer after he moved to Monaco on a free transfer, and Rosell stressed the decision not to renew his deal in Catalunya was purely for sporting reasons.
"Barca made an exquisite gesture with Abidal to renew his deal while he was ill. When he recovered, he was treated as a squad player and the decision was not to renew - merely a sporting decision."